Stable hydrophilic polyurethane foams prepared by using a surfactant soluble in the hydrophilic polyol reactant

ABSTRACT

HYDROPHILIC POLYURETHANE FOAMS WHICH ARE FLEXIBLE AND STABLE, I.E., NON-COLLAPSIBLE AND NON-SHRINKABLE, NON-DISINTEGRATABLE AND CHARACTERIZED BY IMPROVED &#34;WET-OUT&#34; AND &#34;PERCENT VOLUME-SWELL&#34; PROPERTIES, ARE PRODUCED FROM A FOAMABLE POLYURETHANE-FORMING REACTION MIXTURE COMPRISING (A) A HYDROPHILIC POLYOL, (B) A FOAM-STABILIZING AMOUNT OF A SURFACTANT WHICH IS SOLUBLE IN SAID HYDROPHILIC POLYOL AND, IF DESIRED, (C) A FOAM-SHINKAGE INHIBITING AGENT.

March 26, 1974 R. J. LAMPLUGH TAL 3,799,898

STABLE HYDROPHILIC POLYURETHANE FOAMS PREPARED BY USING A SURFACTANTSOLUBLE IN THE .HYDROPHILIC POLYOL REAGTANT Original Filed Jan. 5, 19702 Sheets-Sheet 1 T I 90 I00 TEMPERATURE/ SWELL CURVE TEMPERATURE C Much26, 1974 STABLE HYDROPHILIC P R. J. LAMPLUGH ET AL OLYURETHANE' FOAMSPREPARED BY USING A SURFACTANT SOLUBLE IN THE HYDROPHILIG POLYOLREACTANT Original Filed Jan. 5, 1970 2 Sheets-Sheet 2 TIZIMS 3 UnitedStates Patent STABLE HYDROPHILIC POLYURETHANE FOAMS PREPARED BY USING ASURFACTANT SOLU- BLE IN THE HYDROPHILIC POLYOL REACTANT Roland J.Lamplugh, Chester, and Rocco P. Triolo,

, Broomall, Pa., assignors to Scott Paper Company, Philadelphia, Pa.

Continuation of abandoned application Ser. No. 806, Jan. 5, 1970. Thisapplication Oct. 16, 1972, Ser. No.

Int. Cl. C08g 22/44 US. Cl. 260--2.5 AD 7 Claims ABSTRACT OF THEDISCLOSURE Hydrophilic polyurethane foams which are flexible and stable,i.e., non-collapsible and non-shrinkable, non-disintegratable andcharacterized by improved wet-out and percent volume-swell properties,are produced from a foamable polyurethane-forming reaction mixturecomprising (a) a hydrophilic polyol, (b) a foam-stabilizing amount of asurfactant which is soluble in said hydrophilic polyol and, if desired,a foam-shrinkage inhibiting agent. Y

This is a continuation of application Ser. No. 806, filed Jan. 5, 1970,now abandoned.

BACKGROUND OF THE INVENTION DESCRIPTION OF THE PRIOR ART Polyurethanefoams derived from both polyester and polyether polyols are generallyhydrophobic in nature, i.e., they do not have an atfinity for theabsorption of water. The prior art has, however, disclosed certainmodified polyether polyols suitable for use in foamablepolyurethane-forming reaction mixtures to produce polyurethane foamscharacterized by hydrophilic properties. However, foamablepolyurethane-forming reaction mixtures based on these modified polyetherpolyols suffer the disadvantage of being difficult to process and thefoams produced therefrom are usually non-reproducible, i.e., the foamsdo not have substantially the same hydrophilic and mechanical propertiesand/or are unstable, i.e., the foam does not maintain its cellularintegrity for any reasonable period of time and shrinks or collapses.Various grafting and impregnation methods have also been used in theprior art to produce hydrophilic sponge-like foam materials. Forexample, polymerizable hydrophilic monomers have, been grafted ontohydrophobic polyurethane foam and hydrophilic polymers, such aspolyacrolein have been used to impregnate polyurethane foams. Either agrafting step or an impregnation step would substantially increase thecost of the hydrophilic foam, and the foam obtained thereby is for themost part non-uniform and/or tends to lose its hydrophilicity. There isa long-felt need for stable, reproducible, hydrophilic polyurethane foamsponge suitable for surgical, household and industrial applications.Some of the prior art attempts at solving the problem of making ahydrophilic polyurethane foam have been directed to substitutingnonionic wax-like emulsifiers, such as nonylphenoxypoly-(ethylenoxy)ethanol for the more generally used silicone surfactants.Unfortunately, even the use of these, nonionic surfactants has not beenable to overcome the problem of developing a stable, i.e.,non-collapsible, nonshrinkable hydrophilic polyurethane foam. It is anunfortunate problem in the present stage of development of polyurethanetechnology that the challenge of developing a reproducible, i.e., foamshaving substantially the same hydrophilic and mechanical properties,stable, i.e., noncollapsible and non-shrinkable, hydrophilicpolyurethane foam has not been met.

SUMMARY OF THE INVENTION In accordance with this invention, stable,i.e., noncollapsible and non-shrinkable, reproducible, flexible,cellular hydrophilic polyurethane celliform structures are produced fromfoamable polyurethane-forming reaction mixtures comprising (a) ahydrophilic polyol, (b) a foamstabilizing amount of a surfactant solublein said hydrophilic polyol and, if desired, (c) a foam-shrinkageinhibiting amount of a primary aromatic amine. When an organicpolyisocyanate is reacted with a hydrophilic polyol, defined more fullyhereinbelow, and a surfactant which is soluble in said hydrophilicpolyol and which is also defined more fully hereinbelow, the resultingpolyurethane foam does not shrink or collapse, and is characterized byimproved hydrophilic properties, such as superior wet-out and percentwater-swell" properties, said properties also being defined more fullyhereinbelow.

BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1 and 2 are temperature/ percentswell curves of foams produced in accordance with the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The amount of theabove-mentioned soluble-surfactant contained in the foamablepolyurethane-forming reaction mixture generally ranges from about 0.25part to about 10 parts of surfactant, based on parts by weight ofhydrophilic polyol; the preferred range of soluble-surfactant is fromabout 0.5 part to about 5 parts by weight, based on 100 parts by weightof hydrophilic polyol. Generally foams derived from reaction mixturescontaining less than 0.25 part by weight soluble surfactant tend tocollapse. And foams derived from reaction mixtures containing more than1.5 parts by weight soluble surfactant tend to The hydrophilic foams ofthis invention are celliform structures which may be open-cell,closed-cell or reticulated. By a celliform structure is meant astructure in which at least the outlines of a 3-dimensional cellularstructure are present. The cell walls may be present or they may beremoved. Flexible polyurethane foams, conventionally, upon theirproduction, are open-cell in character. That is to say, the individualdodecahedral cells of the foam body intercommunicate with each other andwith the atmosphere, so that the final product has some degree ofporosity; however, a significant number of cell walls are covered withmembranes of the polyurethane polymer and offer significant impedance toflow therethrough. There are several post-cure techniques for removingthe cell walls, such as by caustic hydrolysis of the cell membranes asdisclosed in US. Pat. 3,171,820 issued to Volz, or by explosiondegradation of the cell membrane as shown in US. Pat. 3,175,025 issuedto Geen et al. The reticulated structures of this invention arecharacterized by improved mechanical properties, such as improvedelongation and tensile and tear strengths. It has also been more fullyhereinbelow.

It has been discovered that the wet-out properties of the foam isimproved at higher levels of surfactant concentration. If desired, ashrinkage-inhibiting agent may be used in combination with thesoluble-surfactant. The use of a shrinkage-inhibiting agent is usuallydesired when the surfactant concentration exceeds about 1.5 parts byweight, based on 100 parts of polyol, because there is a tendency forthe foam to shrink with increasing concentrations of surfactant. Whenfrom about 1 part to about parts by weight of an aromatic primary amine,such as aniline, based on 100 parts by weight of polyol, is used incombination with the soluble surfactants of this invention, it functionsas a shrinkage-inhibiting agent; It has been unexpectedly discoveredthat when aniline is used as a shrinkage-inhibiting agent in combinationwith the abovementioned soluble surfactants, it improves the foamshydrophilic properties, such as wet-out.

At present there is no standard test to measure the wetout property of ahydrophilic foam. For purposes of this invention the wet-out property isdefined as the time required for the absorption of one drop of waterwhich has been gently placed on the surface of a foam sample of 4" x 4"x 2" dimensions. In the wet-out test, five drops of water are gentlyplaced in a random pattern in five separate locations on the same testblock of foam and the 5 water-absorption readings are averaged todetermine the measure of wet-out. It should be noted that there is noforcing or initial impregnation of the foam by the water at the outsetof the test.

In the percent water-swell test, a sample of foam is first cut toapproximately 4" x 4" x 2" and then the actual dimensions of the testblock of foam is precisely measured in centimeters, and the dry-volumeis calculated and recorded. The test sample is then immersed in waterwhich is maintained at 72 F. (22 C.) for minutes. Since it has beendiscovered that volume-swell is dependent upon the temperature of theliquid, it is critical that the wetvolume be measured at a constanttemperature. During the 15-minute test period, the foam is squeezed atrandom intervals to insure complete water wet-out, i.e., completedistribution of water throughout the test block of foam. The test sampleis then measured for a second time to determine its Wet-volume. Thepercent volume-swell (percent VS) is derived from the followingequation:

( Final wt-volumc-initial dry-volume Initial dry-volume percent VS Thesoluble surfactants useful in this invention may be water-soluble andmay also be silicone surfactants, but it is not essential that they beeither water-soluble or silicones. It is necessary only that thesurfactant be soluble in the hydrophilic polyol. In general thesurfactants useful in this invention have a hydrophobic component and ahydrophilic component. The hydrophobic component of the' surfactant maybe derived from aliphatic alcohols, aliphatic mercaptans, aliphaticamines, fatty acids and alkyl;

invention are r and mixtures thereof are also .suitable for use in thisin-.

vention. The hydrophilic component of the surfactant may be derived fromethylene oxide provided that the surfactant is soluble in thehydrophilic polyol. The proportions of ethylene oxide used will dependupon the particular hydrophilic polyol. Representative soluble siliconesurfactants useful in the practice of this invention are L-53l,

L-532 and L-54l0 which are polyoxyalkylene-siloxane coated vegetable oilmanufactured by General Aniline and Film.

:In addition to the novel-shrinkage inhibiting agents, such as aniline,mentioned hereinabove, various other additives may be incorporated inthe polyurethane-i forming composition along with the presentlydisclosed soluble-surfactants, such as fillers pigments, dyes, plasti-'cizers and stabilizers.

The soluble-surfactant and foam-shrinkage inhibiting agent may beadmixed with any one or more of "the several components of the reactantcomposition involved in the making of the polyurethane material. Forexample, the components may be mixed and the reactant componentspolymerized in one place, or the soluble'surfactant, and foam-shrinkageinhibiting agent may be mixed with one or more of the components, i.e.,with the hydrophilic polyol, before mixture with theremainingcomponents. The surfactant may be combined with the polyol, orthe polyisocyanate, or catalyst reactants in any,

of several ways. Each of the polyol, polyisocyanate, catalyst'andsoluble-surfactant may be metered and pumped or charged into a commonmixing vessel, and then the resulting mixture may easily be moved to thepolymeriza tion site for use in molds, slab stock operations, and thelike. It is preferred to carry the soluble-surfactant alone,

/ polyisocyanate with the soluble-surfactant and then comw ene) groups,such as SA1421 manufactured by Dow Chemical Company, X601, X603 and X607manufactured" or in a 'water stream, or mixed with water and a catalyst.The soluble-surfactant may also be admixed with the polyol reactantbefore it is combined with the polyisocyanate reactant. It is alsowithin the scope of the inven-;

tion to mix the soluble-surfactant with the polyisocyanate beforecombining such mixture with the polyol reactant. However, if a catalyst,such as a tertiary amine, and the soluble-surfactant are mixed andallowed to standcat room temperature for substantial periods of time,re-

action may occur. Hence, it is preferred to mix the polyol,-polyisocyanate .and/or catalyst and the soluble-surfactant eithersimultaneously, or to first mix the polyol and/or bine this mixture withthe catalyst. For example, it is sometimes advantageous to prepare apolyol-soluble-sur-- factant mix prior to combining all of theingredients in vention.

For the most part the hydrophilic polyols used in this.

invention are hydrophilic polyether polyols-Representative hydrophilicpolyols useful in this invention are various polyether polyolscontaining a plurality of poly(oxyethylby Olin, and Pluracol 395 and396, PR 7015, PR

Organic polyisocyanates are reacted with the hydro- Broadly, the termpolyisocyanate as used herein, means any of the prior artpolyisocyanates that have been or diethyl dithiophosphate,

could be used to prepare polyurethanes. The term eludes monomeric diandpolyisocyanates and prepolymers of polyols and polyisocyanates where theisocyanate groups are in excess so that there are free availableisocyanate groups available to react with additional polyol. The organicpolyisocyanates useful for the pro duction of the polyurethanes includeethylene diisocyanate, ethylidene diisocyanate,propylene-1,2-diisocyanate, butylene-1,3-diisocyanate, hexylene 1,6diisocyanate, cyclohexylene-l,2-diisocyanate, and the aromaticpolyisocyanates having from 2 to 3 isocyanate groups per molecule andfrom 1 to 3 phenylene rings as the only aromatic cyclic ring systems,such as m-phenylene diisocyanate, 2,4- toluene diisocyanate, 2,6-toluenediisocyanate, 3,3-dimethylas well as various other polyisocyanates suchas 4,4'- biphenylene diisocyanate, 3,3'-dimethoxy-4,4-biphenylenediisocyanate, 3,3-diphenyl-4,4-biphenylene diisocyanate, 4,4-bipheny1enediisocyanate, v 3,3'-dichloro-4,4'-biphenylene diisocyanate,triphenylmethane triisocyanate, 1,5-naphthalene diisocyanate,

and the like.

Useful catalyst or initiator materials which may be used as the catalystcomponent include the tertiary amines, either individually or in mixturelike N-alkylmorpholines, such as N-ethylmorpholine, andN,N-dialkylcyclohexylamines, where the alkyl groups are methyl, ethyl,propyl, butyl, etc., also triethylamine, tripropylamine, tributylamine,triamylamine, pyridine, quinoline, dimethylpiperidine,dimethylhexahydroaniline, diethylhexahydroaniline, the reaction productsof N,N-diethylaminoethanol and phenyl isocyanate, esterimides,1-methyl-4- (dimethylaminoethyl)piperazine, N ethylethylenimine, N,N,N,'-tetramethyl-1,3-butanediamine, triethylamine,2,4,6-tri(dimethylaminomethyl)phenol, tetramethylguanidine,Z-methylpyrazine, dimethylaniline, and nicotine; and metallic compoundsincluding those of bismuth, lead, tin, titanium, iron antimony, uranium,cadmium, cobalt, thorium, aluminum, mercury, zinc, nickel, cerium,molybdenum, vanadium, copper, manganese, zirconium, etc., examples ofwhich include bismuth nitrate, lead 2-ethylhexoate, lead benzoate, leadoleate, sodium trichlorophenate, sodium propionate, lithium acetate,potassium oleate, tetrabutyl tin, butyl tin trichlorate, stannicchloride, tributyl tin l-nonylphenate, stannous octoate, stannousoleate, dibutyl tin di(2-ethylhexoate), di(2- 'ethylhexyl)tin oxide,titanium tetrachloride, tetrabutyl titanate, ferric chloride, antimonytrichloride, cadmium thorium nitrate, triphenylaluminum, nickelocene,etc. The catalyst component either as single compound or as a mixturemay be used in conventional amounts, which usually range from about 0.05to about 4 parts of catalyst per 100 parts of polyolisocyanate reactantsby weight.

In the art and technology of producing polyurethanes, it is also knownto employ what is called prepolymer techniques. This is atechnique'wherein part of the reacis.formed when low boiling liquids, ornormally gaseous tion involved in making a polyurethane is carried outyielding a prepolymer of increased molecular weight and with eitherresultant end groups of hydroxyls or isocyanates depending upon thestoichiometry used in making this prepolymer. This prepolymer is thenused to. prepare the desired final polyurethane product by reacting itwith either a polyisocyanate or one of the desired polyols, depending,as has been mentioned above, on whether the terminal groups of theprepolymer are hydroxyls or isocyanates, respectively. Thesoluble-surfactant of this invention may also be used in the prepolymertechnique of producing polyurethanes.

Polyurethanes are used in both the unfoamed and the so-called foam form.In general, a foamed polyurethane blowing agents, or infiatants aregenerated by or incorporatedjnto the polyurethane-forming reactants.Often the heat of reaction causes these low boiling liquid or gaseousblowing agents to volatilize, thus foaming the composition. In somecases the boiling point of the blowing agent is chosen to be well belowroom temperature, and the composition can be made to foam even beforeany substantial reaction between the polyol and the polyisocyaniatereactants has occurred or before any heat is evolved. This technique issometimes called frothing. Useful blowing agents, i.e., foam-inducingagents, which may be added when foams are desired include water, eitheralone or admixed with other components, e.g., as an aqueous solution ofa tertiary amine catalyst, and the chlorinated and fluorinated alkaneshaving from 1 to about 2 carbon atoms, such as the chlorofiuoromethanesand chlorofluoroethanes, which are commercially available under varioustrademarks, such as Freon manufactured by E. I. du Pont.

The stable hydrophilic foams of this invention are suitable for use invarious applications, uch a houeholdrr,pO sponges, surgical sponges,feminine personal products, components of paper and non-woven laminates,scrubbing devices, disposable cleaning and wiping devices, disposablediapers, rollers for water-base paint, cartridges for absorption ofurine, applicators for deodorants and cosmetics, humidifier elements,and the like.

EXAMPLES To assist those skilled in the art to practice the presentinvention, the following procedures are suggested by way ofillustration, parts and percentages being by weight unless otherwisespecifically noted.

The compositions of the foamable polyurethane-forming reaction mixturesused in the illustrative examples are recited in tabular form. Theingredients of the reaction mixtures are recited in parts per hundredrelative to 100 parts by weight of polyol resin. In the tables, theingredients are identified by their trademarks or a representativesymbol. The polyisocyanate in the reaction mixture is identified asHylene TM, an :20 mixture of the 2,4- and 2,6-isomers of toluenediisocyanate. The ratio of the actual amount of polyisocyanate in thereaction mixture to the theoretical amount of polyisocyanate needed forreaction with all active hydrogen compounds present in the reactionmixture multiplied by is expressed in the tables as Index. Theexpression NEM represents N-ethylmorpholine. The expression X607 is apolyether polyol containing oxyalkylene substituents vended by OlinCorporation. The expressions L-531, L-532 and L-5410 representpolyoxyalkylene-siloxane copolymers vended by'Union Carbide Corporation.The expressions DC-193 and DC-195 represent silicone glycol copolymersvended by Dow Coming. The expression DC-1310" represents apolyoxyalkylenesiloxane copolymer vended by -Dow Corning. The expression77-86 represents a sulfated or sulfonated ethylene oxide-propylene oxidefatty acid adduct vended by Witco Chemical Company. The expressionEL-719 represents a polyoxyethylated' vegetable oil vended by GeneralAniline & Film. The expressions M66-67 and M66-82 represent non-siliconeorganic surfactants vended by Witco Chemical Company.'The expressionfC-6 represents a solution containing one part by weight stannousoctoate and two parts by weight dioctylphthalate vended by WitcoChemical Company. The expression SA1421 represents a polyether polyolcontaining poly(oxyethylene)groups vended by Dow Chemical Company. Theexpressions Pluracol 395 and Pluracol 396, PR 7015 and PR 7048 representpolyether polyols containing poly(oxyethylene) groups in varying amountsvended by Wyandotte Chemical CompanysThe expression PR 7020 representsan amine initiated polyether polyol containing poly(oxyethylene)groupsvended by Wyandotte Chemical Company.

TABLE L-FOAM COMPOSITION Ingredients A B C D E F SA1421.. 100 100 100100 Pluracol 395 80 1 Pluraeol 396 20 100 0.6 0.6 0.6 0.6 1.2 1.2 1.20.1 0.1 0.1 0.1 0.1 0.1 ,0.1 3.0 3.0 3.0 3.0 3.0 3.0 -3.0 31.6 31.6 31.631.6 34.2 34.2 32.5 90 90 90 90 90 p 90 90 a o a. o a o 3. 3. 0

1 Silicone surfactant (soluble in hydrophilic polyol). I Non-siliconesurfactant (soluble in hydrophilic polyol). 1 H

l Silicone surfactant (insoluble in hydrophilic polyol). v Non-siliconesurfactant (insoluble in hydrophilic polyol). Y

Significance-All of the polyurethane foams obtained from thecompositions described in Table I using either soluble siilcone orsoluble non-silicone surfactants were stable, i.e., non-shrinkable andnon-collapsible, and hydrophilic, whereas, those polyurethane foamsobtained from the compositions using either insoluble silicone (foam'C)or insoluble non-silicone (foam D) surfactants were unstable, i.e., theycollapsed. The results of the stability and hydrophilicity tests aregiven in Table H. In Table 11, test foam A corresponds with test foam Aof Table I, etc.

tions useful in the practice of this invention.

TABLE III.FOAM oorvrrosrrroN Ingredients The following Table V givesfoam compositions which illustrate the prior art problem relating tofoam instability.

TABLE V.FOAM COMPOSITION w x 100 100 v10o 0.6 0.6 0.6 0.5 0.5 -0.5 a0 a0va0 31.11 31.0 31.0

Significance-All of the surfactants evaluated in the compositionsdescribed in Table V were insoluble in hydrophilic polyol SA1421. All ofthe polyurethane foams obtained from the compositions described in TableV were unstable, i.e., they collapsed. v

The following Tables VI and VII give the relationship between theconcentration of hydrophilic polyol in the foam composition and thehydrophilic properties of wetout and percent volume-swell of the foamproduced from said composition.

" TABLE VL-FOAM COMPOSITION Significance-In Table In all of the listedsurfactants were soluble in the hydrophilic polyol. of the 'polyurethanefoams obtained from the compositions described in Table 1111 werestable, i.e., non-shrinkable and noncollapsible, and hydrophilic.Hydrophilic properties, especially wet-out times, varied according tothe particular soluble surfactant used in the composition. Table "IV,

Significance-The polyurethane foams obtained from the compositions ofTable VI were all stable, i.e., nonshrinkable and non-collapsible, andexhibited percent volume-swells proportional to the weight percenthydrophilic polyol contained in the composition. In Table VII, test foamA corresponds to test foam A in Table VI, etc. Table VII describes thehydrophilic properties of the foams produced from the compositions ofTable VI.

test foam A corresponds with test foarn' A of Table TABLE VII etc. TableIV describes the hydrophilic properties (wet- Properties A 0' D E F Gout and percent volume-swell) of the foams produced Wet-out,secs 5 1a 5561 120 180 180 3 Percent vo1ume-swe11.--..- 91 40 36 26 23 14 I 0 fromthe compositions of Table III. 1

M'N O P Q R Properties 11 I J. K. I L

Density, 13.0.! 2 3 2.5 2.1 2.1 2.4 2.5 2.6 2.2 2.2 2.2 2.1 2.1

Wet-out, secs 3 180 180 41 180 180 87 180 2 180 3 180 97 111 100 112 06Percent volume-swell.

9 The following Tables VIII and 1X give the relationship between theconcentration of soluble surfactant in the foam composition and thehydrophilic properties of wetout and percent volume-swell of the foamproduced from said composition.

TABLE VIIL-FOAM COMPOSITION 61:. 90 90 100 100 Surfactant: 11-532 0.6 1. 5 1. 0 3. 0

TABLE IX Properties H I J K Wet-out (secs) 59 13 .51 9 Percentvolume-swell 99 99 41 40 The following Tables X and XI show theunexpected advantages obtained when a primary aromatic amine, such asaniline, is added to the foam composition.

TABLE X.-FOAM COMPOSITION L M N 0' 100 100 50 50 50 50 1.0 .05 0. 1 0. 11.2 0.75 0.5 0.5 3.0 1.0 H20 3.0 3.25 3.0 3.0 Hylene TM 35. 6 40. 9 37.2 38. 1 Index 100 100 100 100 Sn rfaetant: L-532 1. 0 1. 0 1. 0 1. 0

TABLE XI Properties L' M N 0' Wet-out (secs) 150 7 101 51 Percent volumeswell 100 93 42 41 The following Tables XH to XIII and FIGS. 1 and 2give the relationship between the percent volume-swell of foams producedin accordance with this invention and the temperature of the solvent,water, used as the test medium.

TABLE XIL-FOAM COMPOSITION Significance.-The two polyurethane foamsobtained from the compositions described in Table XII were stable, i.e.,non-shrinkable and non-collapsible, and hydrophilic. An unexpectedrelationship was discovered when percent volume-swell was studied as afunction of solvent (H O) temperature. The percent volume-swell wasfound to be inversely proportional to solvent (H 0) temperature, i.e.,as the temperature of the H 0 is decreased, the percent volume-swell isincreased. Table XIII describes the relationship between percentvolume-swell and solvent (H O) temperature of the two foams producedfrom the compositions of Table XII. This relationship is furtherdescribed in terms of temperature/percent-swell curves (T/ S) which arerecorded in graphical form in FIGS. 1

- and 2, which show the T/S curve for foams A" and B" respectively ofTable XII.

TABLE XIII.-PERCENT VOLUME-SWELL DATA.

A (percent B (percent volume-swell) volume-swell) Temperature F.)

It is to be understood that changes and variations may be made withoutdeparting from the spirit and scope of this invention as defined by theappended claims.

What is claimed is:

1. A method for producing a flexible, stable hydrophilic polyurethanefoam comprising reacting a polyurethane forming composition comprising(a) a hydrophilic polyether polyol, (b) an organic polyisocyanate, (c)from about 0.25 part to about 10 parts by weight, based on parts byweight of the hydrophilic polyol of a surfactant soluble in saidhydrophilic polyol, (d) a reaction catalyst and (e) a foaming agent.

2. A method as defined in claim 1 wherein the soluble surfactant is asilicone surfactant.

3. A method as defined in claim 1 comprising incorpo rating in thepolyurethane-forming composition from about 1 part to about 10 parts byweight, based on 100 parts by weight of the hydrophilic polyol ofaniline.

4. A flexible, stable, hydrophilic polyurethane celliform structureprepared by the method claimed in claim 1.

5. A polyurethane celliform structure, as claimed in claim 4, furthercharacterized by a uniform water-swell response which is inverselyproportional to incrementally increasing water temperatures.

6. A polyurethane celliform structure, as claimed in claim 4, which is3-dimensionally reticulated.

7. A composition, which, when used in combination with an organicpolyisocyanate, a reaction catalyst and a References Cited UNITED STATESPATENTS 3/1961 Brower 260-25 4/1970 Bailey et al. 260-25 3,285,86611/1966 Gmittel' 260 -2.5

2602.5 G, 25 AH, 2.5 AP- 3,425,999 2/1969 1 3,336,242 8/1967 Hampson eta1. '260s,-'2.5

FOREIGN PATENTS ,825,8 96 8/ l967 ,Great Britainv.. ,--"-j-r; i 2:69:25

DONALD E. CZAJA Primary Exarniner E. C. RZUClDLQ'Assistant Examiner fUS. 01. xgg.

Z222? SIZTATES PATENT OFFICE v v CERTIFICATE OF CORRECTION mum.3;,7'9'9-{8 8 1mm Marc-ii 26, 1974' mm) p i p It is certified that errorappears in the above-identified patent and that said Letters Patent arehereby corrected as shownbelow:

Column 2, line 4, (e th'ylenoxy) should be (e thyleneoxy)h- Column 5,line 65 "stoichiometry" should be --stoichoimetry- Column 6, line v 22"uch a houeholdrr,p0" should be -such J I as householdline 4 2,"mixture" should be -mixtur es Column 7, Table II, 1'22" secondoccurrence, should be --25- "75" should be --72-- Colunm 9; Table VIII,"38.0" should be --38.l-.-

Signed and sealed this 28th day of January 1975.

' (SEAL) v Attest:

McCOY M. GIBSON JR. c. MARSHALL DANN Arresting Officer v Commissioner ofPatents

